過去幾年中,基于超薄薄膜上的曲折納米線在單光子檢測中顯示出巨大的潛力。一方面由于超薄薄膜或納米線的超導(dǎo)特性,器件的性能會大大提升。另一方面,由于高溫超導(dǎo)體在高場超導(dǎo)磁體應(yīng)用中具有較高的T_c和H_c2,所以器件也能在高超導(dǎo)磁場下應(yīng)用。IBS有構(gòu)造高磁場磁體的潛力,未來該磁體可用于領(lǐng)域,例如高能粒子加速器和下一代聚變反應(yīng)堆。因此,對其進(jìn)行He⁺離子輻照作用的研究有極大的興趣。本論文涵蓋了我對薄膜和曲折納米線的制造及其超導(dǎo)性能的研究工作,工作包括一下三部分:第一部分,制備了不同厚度的高質(zhì)量Nb N薄膜。針對不同的場方向測量了上臨界場的溫度和角度依賴性。對于超薄樣品,我們發(fā)現(xiàn)平行于表面方向的上臨界場在接近T_c區(qū)域呈現(xiàn)上彎曲線行為,表明樣品具有二維(2D)性質(zhì),這也從角度依賴性得到證實。并且我們發(fā)現(xiàn)隨著厚度的增加,該特征逐漸減小。其溫度依賴性可以通過基于各向異性Ginzburg Landau理論的模型來描述。有趣的是,在垂直于薄膜表面的場中測得的結(jié)果表明,對于超薄薄膜樣品,在非常窄接近T_c...

【文章頁數(shù)】：141 頁

【學(xué)位級別】：博士

【文章目錄】：
摘要
Abstract
CHAPTER1:Overview of superconductivity
    1.1 Brief history of superconductor
    1.2 London approach
    1.3 Ginzburg-Landau Theory
        1.3.1 G-L equations
        1.3.2 Condensation energy
        1.3.3 Superconducting characteristic lengths
        1.3.4 Interface energy and critical fields
        1.3.5 Surface superconductivity in thin films
    1.4 Research motivation
CHAPTER2:Flux pinning characteristics in superconductors
    2.1 Abrikosov vortex lattice
    2.2 Beans’critical state model
    2.3 Flux pinning forces
    2.4 Elastic modulus of flux line lattice
    2.5 Flux pinning models
        2.5.1 The Kramer model and other models
    2.6 Overview on Nb N and iron based superconductors
CHAPTER3:Fabrication and experimental techniques
    3.1 DC magnetron sputtering
    3.2 Pulsed laser deposition(PLD)
    3.3 Micro-fabrication technology
        3.3.1 Photolithography
        3.3.2 Reaction ion etching(RIE)and lift-off process
    3.4 Sample Characterization
        3.4.1 The X-Ray Diffraction(XRD)characterization
        3.4.2 The X-Ray Reflectivity(XRR)technique
    3.5 Superconducting properties Measurement systems
        3.5.1 Electric Measurements(PPMS)
        3.5.2 Magnetic Measurements(VSM)
CHAPTER4:Study the Hc2 in Nb N thin films of different thickness and Nb Ti N meander wire
    4.1 Abstract
    4.2 Introduction
    4.3 Sample Fabrication
    4.4 Results and Discussion
        4.4.1 X-ray characterization and resistive transition
        4.4.2 Temperature and angular dependence of Hc2

        4.4.3 Enhanced H_c2 in Nb N thick films
        4.4.4 Angular dependence of magneto-resistance
        4.4.5 Current voltage characteristics
    4.5 Summary of the chapter
CHAPTER5:Enhancement of critical current density in He+ion irradiated Ba(Fe,Co)2As2 thin films
    5.1 Abstract
    5.2 Introduction
    5.3 Experimental Details
    5.4 Results and Discussion
        5.4.1 X-ray characterization and resistive transition
        5.4.2 Field dependence of critical current density
        5.4.3 Flux pinning properties
    5.5 Conclusion
CHAPTER6:Flux jumps and study the Jc and flux pinning properties of KCa₂Fe₄As₄F₂ single crystal
    6.1 Introduction
    6.2 Experimental
    6.3 Results and Discussion
    6.4 Summary
CHAPTER7:Summary and Future work
References
List of publications
Conference presentations
Acknowledgements



本文編號：3871039

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